[clang] 6a99326 - [clang] Consistently handle consteval constructors for variables. (#144970)
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Tue Jul 8 14:47:08 PDT 2025
Author: Eli Friedman
Date: 2025-07-08T14:47:04-07:00
New Revision: 6a993264ee0105da32a6a57fb077796076cf6bf4
URL: https://github.com/llvm/llvm-project/commit/6a993264ee0105da32a6a57fb077796076cf6bf4
DIFF: https://github.com/llvm/llvm-project/commit/6a993264ee0105da32a6a57fb077796076cf6bf4.diff
LOG: [clang] Consistently handle consteval constructors for variables. (#144970)
443377a9d1a8d4a69a317a1a892184c59dd0aec6 handled simple variable
definitions, but it didn't handle uninitialized variables with a
consteval constructor, and it didn't handle template instantiation.
Fixes #135281 .
Added:
Modified:
clang/docs/ReleaseNotes.rst
clang/include/clang/Sema/Sema.h
clang/lib/Parse/ParseDecl.cpp
clang/lib/Sema/SemaCoroutine.cpp
clang/lib/Sema/SemaDeclCXX.cpp
clang/lib/Sema/SemaExpr.cpp
clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
clang/test/SemaCXX/cxx2b-consteval-propagate.cpp
Removed:
################################################################################
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index a919f3a71c9cf..8b4f9229c4463 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -920,6 +920,9 @@ Bug Fixes to C++ Support
- Correctly handle allocations in the condition of a ``if constexpr``.(#GH120197) (#GH134820)
- Fixed a crash when handling invalid member using-declaration in C++20+ mode. (#GH63254)
- Fix a crash when trying to instantiate an ambiguous specialization. (#GH51866)
+- Improved handling of variables with ``consteval`` constructors, to
+ consistently treat the initializer as manifestly constant-evaluated.
+ (#GH135281)
Bug Fixes to AST Handling
^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index b281b1cfef96a..a21836dffb0e6 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -6761,6 +6761,7 @@ class Sema final : public SemaBase {
EK_Decltype,
EK_TemplateArgument,
EK_AttrArgument,
+ EK_VariableInit,
EK_Other
} ExprContext;
diff --git a/clang/lib/Parse/ParseDecl.cpp b/clang/lib/Parse/ParseDecl.cpp
index 7e739e09b15e8..c34a1fb6004a9 100644
--- a/clang/lib/Parse/ParseDecl.cpp
+++ b/clang/lib/Parse/ParseDecl.cpp
@@ -2710,6 +2710,7 @@ Decl *Parser::ParseDeclarationAfterDeclaratorAndAttributes(
break;
}
case InitKind::Uninitialized: {
+ InitializerScopeRAII InitScope(*this, D, ThisDecl);
Actions.ActOnUninitializedDecl(ThisDecl);
break;
}
diff --git a/clang/lib/Sema/SemaCoroutine.cpp b/clang/lib/Sema/SemaCoroutine.cpp
index a1389c6c034b1..d193a33f22393 100644
--- a/clang/lib/Sema/SemaCoroutine.cpp
+++ b/clang/lib/Sema/SemaCoroutine.cpp
@@ -783,7 +783,8 @@ static bool checkSuspensionContext(Sema &S, SourceLocation Loc,
const auto ExprContext = S.currentEvaluationContext().ExprContext;
const bool BadContext =
S.isUnevaluatedContext() ||
- ExprContext != Sema::ExpressionEvaluationContextRecord::EK_Other;
+ (ExprContext != Sema::ExpressionEvaluationContextRecord::EK_Other &&
+ ExprContext != Sema::ExpressionEvaluationContextRecord::EK_VariableInit);
if (BadContext) {
S.Diag(Loc, diag::err_coroutine_unevaluated_context) << Keyword;
return false;
diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index f0247f865ba40..a49a8abb677c5 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -18892,7 +18892,8 @@ void Sema::ActOnCXXEnterDeclInitializer(Scope *S, Decl *D) {
EnterDeclaratorContext(S, D->getDeclContext());
PushExpressionEvaluationContext(
- ExpressionEvaluationContext::PotentiallyEvaluated, D);
+ ExpressionEvaluationContext::PotentiallyEvaluated, D,
+ ExpressionEvaluationContextRecord::EK_VariableInit);
}
void Sema::ActOnCXXExitDeclInitializer(Scope *S, Decl *D) {
@@ -18901,29 +18902,6 @@ void Sema::ActOnCXXExitDeclInitializer(Scope *S, Decl *D) {
if (S && D->isOutOfLine())
ExitDeclaratorContext(S);
- if (getLangOpts().CPlusPlus23) {
- // An expression or conversion is 'manifestly constant-evaluated' if it is:
- // [...]
- // - the initializer of a variable that is usable in constant expressions or
- // has constant initialization.
- if (auto *VD = dyn_cast<VarDecl>(D);
- VD && (VD->isUsableInConstantExpressions(Context) ||
- VD->hasConstantInitialization())) {
- // An expression or conversion is in an 'immediate function context' if it
- // is potentially evaluated and either:
- // [...]
- // - it is a subexpression of a manifestly constant-evaluated expression
- // or conversion.
- ExprEvalContexts.back().InImmediateFunctionContext = true;
- }
- }
-
- // Unless the initializer is in an immediate function context (as determined
- // above), this will evaluate all contained immediate function calls as
- // constant expressions. If the initializer IS an immediate function context,
- // the initializer has been determined to be a constant expression, and all
- // such evaluations will be elided (i.e., as if we "knew the whole time" that
- // it was a constant expression).
PopExpressionEvaluationContext();
}
diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 3c3d29c415249..01df1913339d9 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -17934,6 +17934,25 @@ HandleImmediateInvocations(Sema &SemaRef,
Rec.isImmediateFunctionContext() || SemaRef.RebuildingImmediateInvocation)
return;
+ // An expression or conversion is 'manifestly constant-evaluated' if it is:
+ // [...]
+ // - the initializer of a variable that is usable in constant expressions or
+ // has constant initialization.
+ if (SemaRef.getLangOpts().CPlusPlus23 &&
+ Rec.ExprContext ==
+ Sema::ExpressionEvaluationContextRecord::EK_VariableInit) {
+ auto *VD = cast<VarDecl>(Rec.ManglingContextDecl);
+ if (VD->isUsableInConstantExpressions(SemaRef.Context) ||
+ VD->hasConstantInitialization()) {
+ // An expression or conversion is in an 'immediate function context' if it
+ // is potentially evaluated and either:
+ // [...]
+ // - it is a subexpression of a manifestly constant-evaluated expression
+ // or conversion.
+ return;
+ }
+ }
+
/// When we have more than 1 ImmediateInvocationCandidates or previously
/// failed immediate invocations, we need to check for nested
/// ImmediateInvocationCandidates in order to avoid duplicate diagnostics.
diff --git a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
index c6633cbe51cef..70a4c159f9805 100644
--- a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -6103,7 +6103,8 @@ void Sema::InstantiateVariableInitializer(
ContextRAII SwitchContext(*this, Var->getDeclContext());
EnterExpressionEvaluationContext Evaluated(
- *this, Sema::ExpressionEvaluationContext::PotentiallyEvaluated, Var);
+ *this, Sema::ExpressionEvaluationContext::PotentiallyEvaluated, Var,
+ ExpressionEvaluationContextRecord::EK_VariableInit);
currentEvaluationContext().InLifetimeExtendingContext =
parentEvaluationContext().InLifetimeExtendingContext;
currentEvaluationContext().RebuildDefaultArgOrDefaultInit =
diff --git a/clang/test/SemaCXX/cxx2b-consteval-propagate.cpp b/clang/test/SemaCXX/cxx2b-consteval-propagate.cpp
index dd5063cb29c5b..c4cfd9398920a 100644
--- a/clang/test/SemaCXX/cxx2b-consteval-propagate.cpp
+++ b/clang/test/SemaCXX/cxx2b-consteval-propagate.cpp
@@ -576,3 +576,37 @@ int f() {
//expected-note at -2 {{read of non-const variable 'a' is not allowed in a constant expression}}
}
}
+
+#if __cplusplus >= 202302L
+namespace GH135281 {
+ struct B {
+ const void* p;
+ consteval B() : p{this} {}
+ };
+ B b;
+ B b2{};
+ B &&b3{};
+ void f() {
+ static B b4;
+ B b5; // expected-error {{call to consteval function 'GH135281::B::B' is not a constant expression}} \
+ // expected-note {{pointer to temporary is not a constant expression}} \
+ // expected-note {{temporary created here}}
+ }
+ template<typename T> T temp_var_uninit;
+ template<typename T> T temp_var_brace_init{};
+ B* b6 = &temp_var_uninit<B>;
+ B* b7 = &temp_var_brace_init<B>;
+ B* b8 = &temp_var_brace_init<B&&>;
+ template<typename T> void f2() {
+ static T b9;
+ T b10; // expected-error {{call to consteval function 'GH135281::B::B' is not a constant expression}} \
+ // expected-note {{pointer to temporary is not a constant expression}} \
+ // expected-note {{temporary created here}}
+ static B b11;
+ B b12; // expected-error 2 {{call to consteval function 'GH135281::B::B' is not a constant expression}} \
+ // expected-note 2 {{pointer to temporary is not a constant expression}} \
+ // expected-note 2 {{temporary created here}}
+ }
+ void (*ff)() = f2<B>; // expected-note {{instantiation of function template specialization}}
+}
+#endif
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